Nowadays, most USB chargers of battery rods of electronic cigarettes on the market are weak in over-voltage protection of input ends of the USB chargers and over-current protection of output ends of the USB chargers.
The weakness of the over-voltage protection of the input ends of the USB chargers is embodied in that a typical USB charger generally has an over-voltage protection capacity of only 6V. An input voltage that is higher than 6V will generate over-voltage, and may further burn the USB charger and a battery rod of an electronic cigarette being charged by the USB charger.
The weakness of the over-current protection of the output ends of the USB chargers is embodied in that: when an output end of a typical USB charger generates over-current or short-circuit, there is no corresponding protection measure applied to the output end, and excessive output current may burn the USB charger.
Some USB chargers on the market even have no over-voltage and over-current protection functions. When a high voltage is applied to an input end of such a USB charger, the USB charger does not limit the over-voltage, and directly transmits the input voltage to an output end of the USB charger. Thus, a battery rod of an electronic cigarette being charged by the USB charger may be burnt. When the output end of the USB charger generates short-circuit, a power supply connected to the USB charger may malfunction or be burnt because of the absence of short-circuit protection.